Update Tokio to Rust 2018 (#1082)

tokio-signal/examples/multiple.rs

@@ -1,8 +1,6 @@
-//! A small example of how to listen for two signals at the same time
+#![deny(warnings, rust_2018_idioms)]
 
-extern crate futures;
-extern crate tokio;
-extern crate tokio_signal;
+//! A small example of how to listen for two signals at the same time
 
 // A trick to not fail build on non-unix platforms when using unix-specific features.
 #[cfg(unix)]
@@ -11,7 +9,7 @@ mod platform {
     use futures::{Future, Stream};
     use tokio_signal::unix::{Signal, SIGINT, SIGTERM};
 
-    pub fn main() -> Result<(), Box<::std::error::Error>> {
+    pub fn main() -> Result<(), Box<dyn (::std::error::Error)>> {
         // Create a stream for each of the signals we'd like to handle.
         let sigint = Signal::new(SIGINT).flatten_stream();
         let sigterm = Signal::new(SIGTERM).flatten_stream();
@@ -44,11 +42,11 @@ mod platform {
 
 #[cfg(not(unix))]
 mod platform {
-    pub fn main() -> Result<(), Box<::std::error::Error>> {
+    pub fn main() -> Result<(), Box<dyn std::error::Error>> {
         Ok(())
     }
 }
 
-fn main() -> Result<(), Box<std::error::Error>> {
+fn main() -> Result<(), Box<dyn std::error::Error>> {
     platform::main()
 }